Skripal was convicted in Russia of spying for Britain’s MI6 intelligence agency and was sentenced in 2006 for betraying Russian agents

Russia said Tuesday it has not been contacted, but stands ready to cooperate with British authorities investigating the case of a former Russian spy who was hospitalized in critical condition after being exposed to an unknown substance.

British media have identified the man as Sergei Skripal, who was given refuge in Britain after a spy swap between the United States and Russia in 2010.

Kremlin spokesman Dmitry Peskov said Tuesday that what happened is tragic and that the Russian government has no information about the cause.

The 66-year-old Skripal and a woman in her 30s were found unconscious on a bench at a shopping center in the town of

Salisbury on Sunday afternoon.

Local police only identified the two by their approximate ages and said “the pair, who we believe are known to each other, did not have any visible injuries and were taken to Salisbury District Hospital.”

Craig Holden, temporary Assistant Chief Constable of the Wiltshire Police, said: “They are currently being treated for suspected exposure to an unknown substance. Both are currently in a critical condition in intensive care.”

Holden said because the investigation is in its very early stages, “we are unable to ascertain whether or not a crime has taken place.”

Skripal was convicted in Russia of spying for Britain’s MI6 intelligence agency and was sentenced in 2006 for betraying Russian agents to British intelligence. He was pardoned in 2010 as part of a U.S.-Russian spy swap.

Relations between Britain and Russia have been strained since former KGB-agent Alexander Litvinenko was poisoned in London in 2006. A British inquiry concluded Litvinenko was probably killed on the orders of Russian President Vladimir Putin.